In the prior art, it is known that optical information may be recorded or written in a thermoplastic layer by controlling the three parameters of the surface charge density, the light density and the temperature of the thermoplastic layer -- see the A. E. Jvirblis, et al., U.S. Pat. No. 3,795,514. More recently, work has indicated that holographic recording on thermoplastic films may be the basis of future high-density holographic storage of analog and digital data. See the publications "Holographic Recording on Thermoplastic Films," T. C. Lee, Applied Optics, Volume 13, No. 4, April, 1974, pp. 888-895, and "An Experimental Read-Write Holographic Memory," W. C. Stewart, et al., RCA Review, Volume 34, March, 1973, pp. 3-44.
In the past, it was known to apply thermal energy to selective recording areas of a thermoplastic layer using a matrix array of resistive heating elements. This configuration requires at least two electrical connections per selective recording area. Accordingly, in an optical data storage system of reasonable size, the number of electrical connections would be near prohibitive with a significant portion of the area of the thermoplastic layer being required for such electrical connections. In the L. D'Auria U.S. Pat. No. 3,878,515 there is disclosed a thermoplastic storage system wherein each recording area of the thermoplastic layer along a given row is coupled to a pair of electrical busbars, each recording area including an electrical heating element and a photoconducting switching element. When the photoconducting switching element is exposed to a beam of light, the two associated busbars are intercoupled causing current to flow through the electrical heating element and, accordingly, to apply thermal energy to the associated recording area. However, this most recent system still requires that an inordinate portion or amount of the area of the thermoplastic layer be utilized by the busbars and related electrical apparatus including the photoconducting switching element. The present invention is directed toward an apparatus for and a method of eliminating substantially all direct electrical connections to the recording area and to use light beams for the selective writing into the one selected recording area in the thermoplastic layer.